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What is the Universe expanding into..
What is the Universe expanding into..
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View Poll Results: Do you think there was anything before the big bang?
I don't think there was anything before the Big Bang 18 9.05%
I think something existed before the Big Bang 81 40.70%
I don't think the big bang happened 23 11.56%
I think the universe is part of a mutiverse 96 48.24%
Multiple Choice Poll. Voters: 199. You may not vote on this poll

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Old 1st July 2020, 08:33 PM   #3151
Galu is offline Galu  Scotland
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Originally Posted by system7 View Post
But a great film.
Even its science has been analysed! YouTube

"500 turns each and we get to the top!"
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Old 1st July 2020, 08:40 PM   #3152
edbarx is offline edbarx  Malta
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Duality of matter is a weird thing, with particles exhibiting wave like behaviour in certain circumstances, and particle like behaviour in others. A property of any particle is gravitational potential energy. If a particle travels away from an object, it gains gravitational potential energy. Under Quantum Mechanics a photon can be seen as having a mass equivalent to its energy, since mass is energy. The energy of a photon is given by E = hf, where h is Planck's Constant. Using Einstein's E = mc^2, the 'mass' of a photon becomes, m = hf/c^2.

Does a photon exhibit the behaviour of a mass when the dimensions are hugely macroscopic?
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Any fool can make things bigger, more complex, and more violent. It takes a touch of a genius, and a lot of courage, to move in the opposite direction. [Albert Einstein]
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Old 1st July 2020, 08:47 PM   #3153
Just Dave is offline Just Dave  United States
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Originally Posted by Galu View Post
At the end of which I can offer you a 'Moonlight Serenade'!
As a big band trumpet player, I've played bothof those tunes many times.

Thanks for the nice earworms.

Last edited by Just Dave; 1st July 2020 at 08:52 PM.
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Old 1st July 2020, 08:55 PM   #3154
Galu is offline Galu  Scotland
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@ edbarx.

Photons have momentum, given by p = h/λ , where λ is the photon wavelength.

As such, they have the behaviour of mass when it comes to collisions with matter, as is the case in Compton Scattering.
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Old 1st July 2020, 09:12 PM   #3155
Galu is offline Galu  Scotland
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The concept of photons having momentum is more clearly understood in the concept of the solar sail.

A solar sail is a surface thatís attached to lightweight unmanned spacecraft. The sail is designed to reflect incoming photons from the Sun. In doing so, the momenta of the photons is transferred to the sail. This provides a force which pushes the sail, and hence the spacecraft itís attached to, away from the Sun.
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Old 1st July 2020, 09:42 PM   #3156
Galu is offline Galu  Scotland
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@ Steve

Just read your 'Bite every in a hazelnut'. A classic! How do you get away with it?
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Old 6th July 2020, 09:08 PM   #3157
Galu is offline Galu  Scotland
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Default Pluto: Back From The Dead

There was a new programme on the dwarf planet this evening (repeated on BBC2 on Thursday at 11.30pm and available on BBC iPlayer).

The New Horizon space probe flyby in 2015 revealed Pluto to be an active and complex world, with mountains carved from ice, a nitrogen glacier that appeared to be moving and a recently active volcano. Scientists have even started to speculate that there may even be alien life on Pluto today.
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File Type: jpg Pluto and its moon Charon.jpg (69.0 KB, 125 views)
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Old 7th July 2020, 05:15 PM   #3158
system7 is offline system7  United Kingdom
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@ Steve

Just read your 'Bite every in a hazelnut'. A classic! How do you get away with it?
Funny as anything IMO. The Joke is that hindsight is always perfect.

This is an age of miracles and wonders, IMO:

Click the image to open in full size.

I have no wish to go to Pluto. A dull and cold rock, IMO. I have a sensible fear of heights for one thing.

But I am curious if I really saw Apollo 13 fire off to the Moon on Saturday, April 11th. 1970. Apollo 13 - Wikipedia?

I am the first to admit that memory is fallible. But I think I watched Jim Lovell and his buddies fire off to the Moon with my telescope into the Westering evening skies in Epsom, Surrey. 50 years later: Jim Lovell recounts the Apollo 13 disaster | Astronomy.com

Many questions arise. I thought the 2nd or 3rd stage rocket was going right with a puff of smoke. But the new or half-crescent Moon was to the left. Maybe did a lap of Earth orbit before getting on-target.

TBH, maybe I dreamed the whole thing. But I was pretty hot on astronomy in those days. And had many books on the subject.
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Old 7th July 2020, 07:00 PM   #3159
Galu is offline Galu  Scotland
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Quote:
But I am curious if I really saw Apollo 13 fire off to the Moon on Saturday, April 11th. 1970.
The launch azimuth (the direction of the rocket's ground track away from the launch pad) was 72į or about east-northeast (ENE).

Looking at the World Map, I guess it was heading in the direction of the UK - so you may not have been dreaming!
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Old 7th July 2020, 07:32 PM   #3160
Galu is offline Galu  Scotland
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Maybe wasn't the translunar injection that you witnessed though.

I attach the Ground Track during the two parking orbits.

I wonder at what location the burn took place?
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